A nice feature that alot of other MMO's have is kind of a marketplace.
I wouldnt call it an auction house in this game, marketplace would be more suiting.

Here you would be able to place stuff in different "shops" or "containers", and then foreigners would be able to have a look in these and buy the stuff.

For currency you could do it like 10 grass for sale, 10 metal scraps wanted.

Its a rough idea, but could be very usefull..